Mechanism of reduction in hydrogen atmosphere and thermal transformation of synthetic ferrihydrite nanoparticles

Masina, Colani John; Neethling, J.H.; Olivier, E.J.; Ferg, E.E.; Manzini, S.; Lodya, Lonzeche; Mohlala, Pheladi; Ngobeni, M.W.

doi:10.1016/j.tca.2014.11.018

Cited by 15 publications

(10 citation statements)

References 41 publications

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“…It was also worth noting that the Δ E q values (Supporting Information, Table S2) exhibited positive for the samples of Fh‐RT, Fh‐150, and Fh‐200, whereas they converted to negative values instead for the samples of Fh‐250, Fh‐300. Namely, the charge distribution symmetry of structure unit inside Fh varies from long ellipsoid to oblate ellipsoid owing to phase transformation during dehydration process [24a, 25] . Furthermore, the samples of Fh‐RT, Fh‐150 and Fh‐200 demonstrated non‐magnetic property while those samples annealed at higher temperatures (Fh‐250, Fh‐300) showed strong magnetic field intensity of nearly 50 T (Supporting Information, Table S2).…”

Section: Resultsmentioning

confidence: 99%

Unveiling the Hydration Structure of Ferrihydrite for Hole Storage in Photoelectrochemical Water Oxidation

et al. 2021

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Ferrihydrite (Fh) has been demonstrated acting as a hole‐storage layer (HSL) in photoelectrocatalysis system. However, the intrinsic structure responsible for the hole storage function for Fh remains unclear. Herein, by dehydrating the Fh via a careful calcination, the essential relation between the HSL function and the structure evolution of Fh material is unraveled. The irreversible and gradual loss of crystal water molecules in Fh leads to the weakening of the HSL function, accompanied with the arrangement of inner structure units. A structure evolution of the dehydration process is proposed and the primary active structure of Fh for HSL is identified as the [FeO6] polyhedral units bonding with two or three molecules of crystal water. With the successive loss of chemical crystal water, the coordination symmetry of [FeO6] hydration units undergoes mutation and a more ordered structure is formed, causing the difficulty for accepting photogenerated holes as a consequence.

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Section: Resultsmentioning

confidence: 99%

Unveiling the Hydration Structure of Ferrihydrite for Hole Storage in Photoelectrochemical Water Oxidation

et al. 2021

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“…31 The details of the synthesis route are described in ref. 32. Nanoparticles of 2LFh were found to be of poor crystallinity with average crystallite size of $4.0, while 6LFh was found to be of a relatively better crystallinity with an average crystallite size of $6.0 nm.…”

Section: Sample Descriptionmentioning

confidence: 94%

Structural and magnetic properties of ferrihydrite nanoparticles

et al. 2015

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“…Wüstite is expected to undergo disproportionation at temperatures below 567°C [19], forming magnetite and iron. The absence of iron in the diffractogram at this temperature suggests that the wüstite is being stabilised by some factor, most likely a high water to hydrogen molar ratio within its local vicinity [20] suggesting that here the presence of silica is inhibiting magnetite formation [28].…”

Section: Xrdmentioning

confidence: 96%

“…The absence of iron in the diffractogram at this temperature suggests that the wüstite is being stabilised by some factor, most likely a high water to hydrogen molar ratio within its local vicinity [20] [21] [22] [23] or a result of the slow kinetics which govern the disproportionation [24]. Metallic iron (α- suggesting that here the presence of silica is inhibiting magnetite formation [28].…”

Section: Xrdmentioning

confidence: 99%

Iron-silica interaction during reduction of precipitated silica-promoted iron oxides using in situ XRD and TEM

Coombes

Olivier

Prestat

et al. 2021

Applied Catalysis A: General

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The effect of silica-promotion on the reduction of iron oxides in hydrogen was investigated using in situ X-ray diffraction and aberration-corrected transmission electron microscopy to understand the mechanism of reduction and the identity of the iron(II) silicate phase that has historically been designated as the cause of the iron-silica interaction in such materials. In the absence of a silica promoter the reduction of hematite to α-Fe proceeds via magnetite. Silica promoted amorphous iron oxide is reduced to α-Fe via stable magnetite and wüstite phases. During reduction of silica-promoted iron oxide, Fe 0 diffuses out of the amorphous silicapromoted iron oxide matrix upon reduction from Fe 2+ and coexists with an amorphous Fe-O-Si matrix. Certain portions of wüstite remain difficult to reduce to α-Fe owing to the formation of a protective silica-containing layer covering the remaining iron oxide regions. Given sufficient energy, this amorphous Fe-O-Si material forms ordered, crystalline fayalite.

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Mechanism of reduction in hydrogen atmosphere and thermal transformation of synthetic ferrihydrite nanoparticles

Cited by 15 publications

References 41 publications

Unveiling the Hydration Structure of Ferrihydrite for Hole Storage in Photoelectrochemical Water Oxidation

Unveiling the Hydration Structure of Ferrihydrite for Hole Storage in Photoelectrochemical Water Oxidation

Structural and magnetic properties of ferrihydrite nanoparticles

Iron-silica interaction during reduction of precipitated silica-promoted iron oxides using in situ XRD and TEM

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